An Associated Press analysis found that there are thousands of laws, rules and regulations at the local, county, state and federal levels. The laws and rules vary by state, and even within states, according to a 2011 compilation of state gun laws by the Bureau of Alcohol, Tobacco, Firearms and Explosives.

These laws and regulations govern who can carry a firearm, what kind of firearm is legal, the size of ammunition magazines, and more. In some places, a person can buy as many guns as desired.

Not only can people acquire military-style assault weapons, they can also get gangster-style Tommy guns, World War II-era bazookas and even sawed-off shotguns.

“If you regulate something on the local or state level, you are still a victim to guns coming into other localities or states,” said Laura Cutilletta, a senior staff attorney at the California-based Law Center to Prevent Gun Violence.

In California, most guns come from Nevada, where there is almost no regulation of firearms, Cutilletta said, and in Arizona, gun owners don’t need a permit.

President Barack Obama earlier this month announced a $500 million plan to tighten federal gun laws. The December shooting massacre in Newtown, Conn., that killed 20 children and six adults at an elementary school launched the issue of gun control policy to a national focus not seen in decades.

Obama is urging Congress to pass new laws, some of which would set a minimum standard for the types of firearms and ammunition that are commercially available. Sen. Dianne Feinstein, D-Calif., on Thursday said she was introducing a new assault weapons ban.

The powerful gun lobby says the problem lies in enforcement of existing laws.

“Which begs the question: Why are we putting more laws on the books if we’re not enforcing the laws we already have on the books?” said Andrew Arulanandam, spokesman for the National Rifle Association.

New gun laws will face tough opposition in Congress, particularly from members who rely on the NRA during election campaigns. The NRA contributed more than $700,000 to members of Congress during the 2012 election cycle, according to the Center for Responsive Politics.

Recognizing the opposition in Congress, states already are passing their own new gun laws while officials from some states are promising to ignore any new federal mandates. As the national debate on gun control and Second Amendment rights escalates, the terms being used won’t mean the same thing everywhere, due to the thousands of laws, rules and regulations across the country.

“The patchwork of laws in many ways means that the laws are only as effective as the weakest law there is,” said Gene Voegtlin of the International Association of Chiefs of Police. “Those that are trying to acquire firearms and may not be able to do that by walking into their local gun shop will try to find a way to do that. This patchwork of laws allows them to seek out the weak links and acquire weapons.”

Obama wants to address this, in part, by passing federal gun-trafficking laws that carry heavy penalties. It’s difficult to crack down on trafficking because the penalties are too low to serve as a deterrent, and federal prosecutors decline many cases because of a lack of evidence. For instance, in order to charge someone with willfully participating in a business of selling firearms without a license, the ATF needs to prove that the guns were not sold out of the suspect’s private collection, the Justice Department inspector general has said.

Obama has also called for a new federal law banning magazines that carry more than 10 rounds of ammunition — a measure that was in effect during the previous assault weapons ban, between 1994 and 2004. High-capacity magazines have been used in recent deadly mass shootings, including those in Newtown, and in the suburban Denver movie theater attack last summer.

A high-capacity ammunition magazine means different things in different places

In California, considered by many to have some of the strongest gun laws in the country, a large-capacity magazine is one that holds more than 10 rounds. In Illinois there is no state law regarding magazines. Yet, there are laws regarding magazines in Chicago where the threshold is more than 12 rounds. But about 40 miles away in Aurora, Ill., this type of magazine is called a large-capacity ammunition feeding device and means anything more than 15 rounds.

In 44 states, including Arizona, Colorado, Connecticut, Texas and Virginia where these magazines have been used in deadly mass shootings, there are no laws against using them, according to a 2012 analysis by the Law Center to Prevent Gun Violence. If a federal law banned magazines that hold more than 10 rounds, it would become the minimum standard.

The definition of “assault weapon” also varies. There is no federal definition of an assault weapon, and the meaning of the term is inconsistent even within the gun industry. California defines an assault weapon as a “firearm (that) has such a high rate of fire and capacity for fire-power that its function as a legitimate sports or recreational firearm is substantially outweighed by the danger that it can be used to kill and injure human beings.” The law specifically lists 60 rifles, 14 pistols and five shotguns. Neighboring states Nevada and Arizona have no assault weapon restrictions.

Federal law does not prohibit the ownership of any weapon, said Ginger Colbrun, a Bureau of Alcohol, Tobacco, Firearms and Explosives spokeswoman in Washington. In order to buy or own certain firearms, including automatic weapons, machine guns and bazookas, people do have to apply for permission from the federal government. But as long as the application for a restricted firearm is approved, and there is no state law barring ownership of that type of gun, it’s legal.

“There is such a variation in the number of laws that regulate the distribution of guns that there is no adequate minimum standard,” said Richard Aborn, president of the New York-based Citizens Crime Commission. “The federal government has an obligation to establish at least minimum standards that have to be complied with before a gun can be sold anywhere in America.”